JP3971478B2 - Method for detecting decompression tire in vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting a decompressed tire in a vehicle, which is suitable for passenger cars, trucks, buses, and the like.
[0002]
[Prior art]
Conventional methods detect tires that have been deflated or partially deflated by comparing tire turning radii. Such systems utilize wheel speed signals, such as signals from an electronic anti-lock-brake system (ABS), comparing each wheel signal in various ways, and one wheel is significantly faster than the other. It is determined whether or not it is rotating, which means that the radius of rotation has been reduced by the decompression of the tire.
[0003]
[Problems to be solved by the invention]
However, in the case of a tire that has been deflated or partially deflated, the inventor of the present application has an increase in centrifugal force acting on the tread portion of the radially outer circumference of the tire, so that the radius of rotation increases with the rotational speed. We found that it increased significantly. This phenomenon can occur to a very limited extent even in tires that are normally inflated, but this is clearly the case with decompression tires where the tread is not restrained by the tension on the casing ply. The degree gets bigger.
[0004]
As a result, the difference in speed signal that the reduced pressure alarm system compares to detect the reduced pressure decreases as the vehicle speed increases. In fact, if the vehicle speed is very high, the decompression tire can be larger than the diameter of a normally inflated tire, so that the decompression alarm system will clearly depressurize other normal pressure tires. It has been found that it may be detected that
[0005]
Accordingly, it is an object of the present invention to provide a method for detecting decompression tires in a moving vehicle that maintains the required sensitivity even when the vehicle speed increases without issuing a false alarm.
[0006]
[Means for Solving the Problems]
The method for detecting a deceleration tire in a vehicle according to the present invention compares the angular velocity signal values C1, C2, C3, and C4 from the wheel speed sensors at the left front wheel, right front wheel, left rear wheel, and right rear wheel. A method for detecting a decompression tire in a vehicle by comparing turning radii, the detection method comprising:
The four angular velocity signal values C1-C4 are processed by the central processing unit, and the sum of the signal values from the wheels on the other pair of diagonal lines is subtracted from the sum of the signal values from the wheels on the other pair of diagonal lines, The result is expressed as a percentage of the average value of the sum DEL ′ = (C1 + C 4 −C2−C3) × 50 /
[(C1 + C2 + C3 + C4) / 4]
And calculating the error value DEL ′ in normal driving, and whether the error value DEL ′ is between a DEL′MIN value of 0.05 and a DEL′MAX value of 0.5 detects whether, and, if the DEL 'is in the range to determine which tire is apparently reduced pressure by comparing with one another the tire angle velocity signal values C1-C4, the end of the vehicle tire Operating the alarm indicator to warn the driver that a particular tire is depressurized;
As a step in which DEL ′ is corrected before the determination of the DEL ′ range,
From the wheel speed signal value C1-C4, the vehicle speed SP D represented by the following equation:
SPD = (C1 + C2 + C3 + C4) / (4 × KPHFAC)
(However, KPHFAC is a constant that represents the number of wheel speed signals for each wheel speed sensor per speed unit.)
A step of determining
In the DEL ′ calculation step, an error value DEL ′ is calculated for each constant speed,
The vertical axis of the ratio obtained by dividing DEL 'at each constant speed CSP1-CSPn by the error value DEL' at the reference speed REFSPD, and the horizontal axis of the square of the ratio SPQT obtained by dividing each constant speed CSP1-CSPn by the reference speed REFSPD Plot a 2D Cartesian graph with values,
Determine the best straight line through the points on the diagram,
The SPDELFAC is a rate factor determined by a calibration procedure consisting of reading from the graph as an intercept above 1.0 on the vertical axis when SPNS is zero,
In the calibration procedure, the correction error value DEL is repeatedly calculated by dividing the calculated error value DEL ′ by the correction coefficient SPDELCOR during normal driving, and the error is determined in order to determine whether or not the tire is depressurized. Instead of the value DEL ', a correction error value DEL calculated with respect to the vehicle speed at that time is used .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Further features of the present invention will be apparent from the following description of embodiments with the aid of the accompanying drawings, which are merely exemplary.
[0008]
FIG. 1 is a schematic diagram illustrating a decompression alarm device for a vehicle having four wheels, and FIG. 2 is a schematic diagram illustrating determination of a speed coefficient SPDELFAC by a graphical method.
[0009]
The apparatus shown in FIG. 1 provides a decompression reporting device for a vehicle having four wheels 1, 2, 3, and 4. Wheels 1 and 2 are left front and right front wheels, respectively, and wheels 3 and 4 are left rear and right rear wheels, respectively. Each wheel has a gearing associated with the wheel, which consists of a magnetic pickup of the type used for electronic vehicle anti-skid devices (commonly known as ABS brake systems). Of the kind designed and adapted to supply digital signals. In this case, each pickup is further connected to a decompression warning detection device using a digital signal similar to the ABS system.
[0010]
The electronic signals from each of the four wheels are sent via cable 5 to four independent inputs 6, 7, 8 and 9 of a central processing unit (CPU) 10. Four independent indicator lights 12, 13, 14 and 15 are provided, one for each wheel 1, 2, 3 and 4. These indicator lights can be installed on the vehicle dashboard for the most convenience.
[0011]
The central processing unit 10 is basically a microprocessor that monitors four signals and determines whether an external signal should be sent to operate an indicator light warning a decompressed tire. Compare the four signals. If the vehicle is already equipped with an ABS system, the microprocessor 10 may be the same microprocessor as the ABS system. Another microprocessor may be provided.
[0012]
The values of all digital pulse signals from each of the wheels 1, 2, 3 and 4 for 5 seconds are C1, C2, C3 and C4, respectively. The central processing unit 10 calculates these values as described below to determine whether to send a decompression warning signal to one of the indicator lights 12, 13, 14 or 15.
[0013]
The method of the present invention proceeds by processing the four angular velocity signal values C1-C4 in the central processing unit 10 to determine the error value DEL ′ in normal driving, and this processing is performed on a pair of diagonal wheels. The sum of the signal values from the other pair of diagonal wheels is subtracted from the sum of the signal values from, and the result is used as a percentage of the average value of the sum, for example, DEL '= (C1 + C2-C2-C3) × 50 / [(C1 + C2 + C3 + C4) / 4]
It is performed by expressing.
[0014]
However, since the magnitude of the error value DEL ′ decreases with speed, the speed signal values C1-C4 of the four wheels are averaged and divided by the constant KPHFAC, which is the number of wheel speed signals per wheel sensor per speed unit. The vehicle speed SPD is determined as follows,
SPD = (C1 + C2 + C3 + C4) / (4 × KPHFAC)
Next, it is necessary to correct the DEL ′ value by the correction coefficient SPDELCOR to obtain a correction error value DEL.
[0015]
The correction coefficient SPDELCOR is applied to the three wheels, for example, the wheels 2, 3 and 4, with the air up to the normal schedule pressure and the remaining tires being decompressed, at a plurality of n constant speeds CSP1-CSPn. It is determined from a correction procedure that consists of running in a straight line. The plurality of constant speeds CSP1-CSPn desirably include a specific speed substantially over the speed range capability of the vehicle and selected as the reference speed REFSPD. The constant speed CSP1-CSPn is, for example, 60, 80, 100, 120, 140, 160 kph and more, and the reference speed REFSPD is preferably 120 kph. The decompression tire is desirably decompressed by 30% of its normal pressure.
[0016]
At each constant speed CSP1-CSPn, the wheel speed values C1-C4 are monitored and an error value DEL ′ is calculated. Next, for each of the n constant speeds, the ratio DELCORQOT of the error value DEL 'at that speed divided by the error value DEL' at the reference speed REFSPD and the ratio SPDQOT of the constant speed divided by the reference speed REFSPD are determined. The Next, as shown in FIG. 2, for each constant speed CSP1-CSPn, a two-dimensional Cartesian XY graph of DDLCORQOT values plotted on the vertical Y axis versus square of SPDQOT values plotted on the horizontal X axis is shown. available.
[0017]
Next, the determination procedure draws or derives a straight line BSTRL that represents the optimum value through the data points of the graph, each corresponding to a constant velocity CSP1-CSPn, by another means such as least squares. Proceed to The velocity factor SPDELFAC is then set equal to the intercept above 1.0 of the straight line BSTR on the Y axis of DELCORQOT as shown in FIG.
[0018]
Next, the correction coefficient SPDELCOR is determined using SPDELFAC from the following relationship.
[0019]
SPDELCOR = 1.0 + [SPDELFAC × (1-SPNS)]
Here, SPNS is a speed number square which is the square of the ratio of the vehicle speed SPD and the reference speed REFSPD. Thus, the corrected error value DEL is obtained from the following relationship.
[0020]
DEL = DEL '/ SPDELCOR
The central processing unit 10 then executes a step of determining whether the magnitude of the correction error value DEL is between a minimum value of 0.05 and a maximum value of 0.5. In the meantime, the central processing unit performs another step of comparing the angular velocity signal values C1-C4 of the wheels with each other to determine which wheel is rotating fastest. The vehicle tire warning indicator is activated to warn the driver that the wheel tire has been depressurized.
[0021]
In a preferred method, the calibration procedure is carried out using the tire of the wheel 1 that has been partially depressurized.
[0022]
In a further preferred method, the calibration procedure is repeated four times, each time using different tires that are partially depressurized and determining the value of the individual speed factor SPDELFAC for each wheel. Next, when it is detected that the value of the error value DEL ′ is in the range of 0.05 to 0.5, the central processing unit compares the wheel speed to determine which is the decompression tire. The method is modified to determine the corrected error value DEL using the specific value of the speed factor SPDELFAC for that wheel.
[0023]
Accordingly, the present invention provides a method for detecting a decompressed tire in a vehicle that maintains the required sensitivity as speed increases.
[0024]
【The invention's effect】
According to the method of the present invention, even if the vehicle speed increases, a false alarm is not issued and the necessary sensitivity can be maintained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a depressurization alarm device for a vehicle having four wheels.
FIG. 2 is a schematic diagram illustrating the determination of a speed factor SPDELFAC by a graphical method.
[Explanation of symbols]
1, 2, 3, 4 Wheel 10 Central processing unit 12, 13, 14, 15 Indicator light

Claims (4)

Comparison of angular velocity signal values C1, C2, C3 and C4 from wheel speed sensors at the left front wheel, right front wheel, left rear wheel and right rear wheel, and comparison of tire turning radii, A detection method comprising:
The four angular velocity signal values C1-C4 are processed by the central processing unit, and the sum of the signal values from the wheels on the other pair of diagonal lines is subtracted from the sum of the signal values from the wheels on the other pair of diagonal lines, The result is expressed as a percentage of the average value of the sum. DEL ′ = (C1 + C 4 −C2−C3) × 50 /
[(C1 + C2 + C3 + C4) / 4]
And calculating the error value DEL ′ in normal driving, and whether the error value DEL ′ is between a DEL′MIN value of 0.05 and a DEL′MAX value of 0.5 detects whether, and, if the DEL 'is in the range to determine which tire is apparently reduced pressure by comparing with one another the tire angle velocity signal values C1-C4, the end of the vehicle tire Operating the alarm indicator to warn the driver that a particular tire is under pressure,
Furthermore, as a step in which DEL ′ is corrected before the determination of the DEL ′ range,
From the wheel speed signal value C1-C4, the vehicle speed SP D represented by the following equation:
SPD = (C1 + C2 + C3 + C4) / (4 × KPHFAC)
(However, KPHFAC is a constant that represents the number of wheel speed signals for each wheel speed sensor per speed unit.)
A step of determining
The correction coefficient SPDELCOR is given by
SPDELCOR = 1.0 + [SPDELFAC × (1-SPNS)]
Steps determined by:
The SPNS is the square of the ratio of the vehicle speed SPD and the reference speed REFSPD, that is, the square of the speed coefficient of SPNS = (SPD / REFSPD) × (SPD / REFSPD), and the SPDELFAC is
Three wheels with a constant speed CSP1-CSPn of n, including substantially the entire speed range capability and including the reference speed REFSPD, with air up to normal schedule pressure and the remaining tires reduced. Run straight,
In the DEL ′ calculation step, an error value DEL ′ is calculated for each constant speed,
The vertical axis of the ratio obtained by dividing DEL 'at each constant speed CSP1-CSPn by the error value DEL' at the reference speed REFSPD, and the horizontal axis of the square of the ratio SPQT obtained by dividing each constant speed CSP1-CSPn by the reference speed REFSPD Plot a 2D Cartesian graph with values,
Determine the best straight line through the points on the diagram,
The SPDELFAC is a rate factor determined by a calibration procedure consisting of reading from the graph as an intercept above 1.0 on the vertical axis when SPNS is zero,
In the calibration procedure, the correction error value DEL is repeatedly calculated by dividing the calculated error value DEL ′ by the correction coefficient SPDELCOR during normal driving, and the error is determined in order to determine whether or not the tire is depressurized. A method of using a corrected error value DEL calculated for the current vehicle speed instead of the value DEL ′ . In the calibration procedure, the method of claim 1 Symbol mounting the tire of the wheel 1 is partially reduced pressure. The method according to claim 1 or 2 , wherein the reference speed REFSPD is 120 kph. When the speed factor SPDELFAC is determined for all four wheels 1-4 of the vehicle and it is recognized that a particular wheel is depressurized, the SPDELLCOR is calculated using the corresponding SPDELFAC to correct the error value DEL ' The method according to claim 1 , 2 or 3 .

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